x86: relax RAM check in ioremap()

[wrt350n-kernel.git] / arch / ppc / 8260_io / enet.c

/*
 * Ethernet driver for Motorola MPC8260.
 * Copyright (c) 1999 Dan Malek (dmalek@jlc.net)
 * Copyright (c) 2000 MontaVista Software Inc. (source@mvista.com)
 *      2.3.99 Updates
 *
 * I copied this from the 8xx CPM Ethernet driver, so follow the
 * credits back through that.
 *
 * This version of the driver is somewhat selectable for the different
 * processor/board combinations.  It works for the boards I know about
 * now, and should be easily modified to include others.  Some of the
 * configuration information is contained in <asm/cpm1.h> and the
 * remainder is here.
 *
 * Buffer descriptors are kept in the CPM dual port RAM, and the frame
 * buffers are in the host memory.
 *
 * Right now, I am very watseful with the buffers.  I allocate memory
 * pages and then divide them into 2K frame buffers.  This way I know I
 * have buffers large enough to hold one frame within one buffer descriptor.
 * Once I get this working, I will use 64 or 128 byte CPM buffers, which
 * will be much more memory efficient and will easily handle lots of
 * small packets.
 *
 */
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/string.h>
#include <linux/ptrace.h>
#include <linux/errno.h>
#include <linux/ioport.h>
#include <linux/slab.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/skbuff.h>
#include <linux/spinlock.h>
#include <linux/bitops.h>

#include <asm/immap_cpm2.h>
#include <asm/pgtable.h>
#include <asm/mpc8260.h>
#include <asm/uaccess.h>
#include <asm/cpm2.h>
#include <asm/irq.h>

/*
 *                              Theory of Operation
 *
 * The MPC8260 CPM performs the Ethernet processing on an SCC.  It can use
 * an aribtrary number of buffers on byte boundaries, but must have at
 * least two receive buffers to prevent constant overrun conditions.
 *
 * The buffer descriptors are allocated from the CPM dual port memory
 * with the data buffers allocated from host memory, just like all other
 * serial communication protocols.  The host memory buffers are allocated
 * from the free page pool, and then divided into smaller receive and
 * transmit buffers.  The size of the buffers should be a power of two,
 * since that nicely divides the page.  This creates a ring buffer
 * structure similar to the LANCE and other controllers.
 *
 * Like the LANCE driver:
 * The driver runs as two independent, single-threaded flows of control.  One
 * is the send-packet routine, which enforces single-threaded use by the
 * cep->tx_busy flag.  The other thread is the interrupt handler, which is
 * single threaded by the hardware and other software.
 */

/* The transmitter timeout
 */
#define TX_TIMEOUT      (2*HZ)

/* The number of Tx and Rx buffers.  These are allocated from the page
 * pool.  The code may assume these are power of two, so it is best
 * to keep them that size.
 * We don't need to allocate pages for the transmitter.  We just use
 * the skbuffer directly.
 */
#define CPM_ENET_RX_PAGES       4
#define CPM_ENET_RX_FRSIZE      2048
#define CPM_ENET_RX_FRPPG       (PAGE_SIZE / CPM_ENET_RX_FRSIZE)
#define RX_RING_SIZE            (CPM_ENET_RX_FRPPG * CPM_ENET_RX_PAGES)
#define TX_RING_SIZE            8       /* Must be power of two */
#define TX_RING_MOD_MASK        7       /*   for this to work */

/* The CPM stores dest/src/type, data, and checksum for receive packets.
 */
#define PKT_MAXBUF_SIZE         1518
#define PKT_MINBUF_SIZE         64
#define PKT_MAXBLR_SIZE         1520

/* The CPM buffer descriptors track the ring buffers.  The rx_bd_base and
 * tx_bd_base always point to the base of the buffer descriptors.  The
 * cur_rx and cur_tx point to the currently available buffer.
 * The dirty_tx tracks the current buffer that is being sent by the
 * controller.  The cur_tx and dirty_tx are equal under both completely
 * empty and completely full conditions.  The empty/ready indicator in
 * the buffer descriptor determines the actual condition.
 */
struct scc_enet_private {
        /* The saved address of a sent-in-place packet/buffer, for skfree(). */
        struct  sk_buff* tx_skbuff[TX_RING_SIZE];
        ushort  skb_cur;
        ushort  skb_dirty;

        /* CPM dual port RAM relative addresses.
        */
        cbd_t   *rx_bd_base;            /* Address of Rx and Tx buffers. */
        cbd_t   *tx_bd_base;
        cbd_t   *cur_rx, *cur_tx;               /* The next free ring entry */
        cbd_t   *dirty_tx;      /* The ring entries to be free()ed. */
        scc_t   *sccp;
        struct  net_device_stats stats;
        uint    tx_full;
        spinlock_t lock;
};

static int scc_enet_open(struct net_device *dev);
static int scc_enet_start_xmit(struct sk_buff *skb, struct net_device *dev);
static int scc_enet_rx(struct net_device *dev);
static irqreturn_t scc_enet_interrupt(int irq, void *dev_id);
static int scc_enet_close(struct net_device *dev);
static struct net_device_stats *scc_enet_get_stats(struct net_device *dev);
static void set_multicast_list(struct net_device *dev);

/* These will be configurable for the SCC choice.
*/
#define CPM_ENET_BLOCK  CPM_CR_SCC1_SBLOCK
#define CPM_ENET_PAGE   CPM_CR_SCC1_PAGE
#define PROFF_ENET      PROFF_SCC1
#define SCC_ENET        0
#define SIU_INT_ENET    SIU_INT_SCC1

/* These are both board and SCC dependent....
*/
#define PD_ENET_RXD     ((uint)0x00000001)
#define PD_ENET_TXD     ((uint)0x00000002)
#define PD_ENET_TENA    ((uint)0x00000004)
#define PC_ENET_RENA    ((uint)0x00020000)
#define PC_ENET_CLSN    ((uint)0x00000004)
#define PC_ENET_TXCLK   ((uint)0x00000800)
#define PC_ENET_RXCLK   ((uint)0x00000400)
#define CMX_CLK_ROUTE   ((uint)0x25000000)
#define CMX_CLK_MASK    ((uint)0xff000000)

/* Specific to a board.
*/
#define PC_EST8260_ENET_LOOPBACK        ((uint)0x80000000)
#define PC_EST8260_ENET_SQE             ((uint)0x40000000)
#define PC_EST8260_ENET_NOTFD           ((uint)0x20000000)

static int
scc_enet_open(struct net_device *dev)
{

        /* I should reset the ring buffers here, but I don't yet know
         * a simple way to do that.
         */
        netif_start_queue(dev);
        return 0;                                       /* Always succeed */
}

static int
scc_enet_start_xmit(struct sk_buff *skb, struct net_device *dev)
{
        struct scc_enet_private *cep = (struct scc_enet_private *)dev->priv;
        volatile cbd_t  *bdp;


        /* Fill in a Tx ring entry */
        bdp = cep->cur_tx;

#ifndef final_version
        if (bdp->cbd_sc & BD_ENET_TX_READY) {
                /* Ooops.  All transmit buffers are full.  Bail out.
                 * This should not happen, since cep->tx_full should be set.
                 */
                printk("%s: tx queue full!.\n", dev->name);
                return 1;
        }
#endif

        /* Clear all of the status flags.
         */
        bdp->cbd_sc &= ~BD_ENET_TX_STATS;

        /* If the frame is short, tell CPM to pad it.
        */
        if (skb->len <= ETH_ZLEN)
                bdp->cbd_sc |= BD_ENET_TX_PAD;
        else
                bdp->cbd_sc &= ~BD_ENET_TX_PAD;

        /* Set buffer length and buffer pointer.
        */
        bdp->cbd_datlen = skb->len;
        bdp->cbd_bufaddr = __pa(skb->data);

        /* Save skb pointer.
        */
        cep->tx_skbuff[cep->skb_cur] = skb;

        cep->stats.tx_bytes += skb->len;
        cep->skb_cur = (cep->skb_cur+1) & TX_RING_MOD_MASK;

        spin_lock_irq(&cep->lock);

        /* Send it on its way.  Tell CPM its ready, interrupt when done,
         * its the last BD of the frame, and to put the CRC on the end.
         */
        bdp->cbd_sc |= (BD_ENET_TX_READY | BD_ENET_TX_INTR | BD_ENET_TX_LAST | BD_ENET_TX_TC);

        dev->trans_start = jiffies;

        /* If this was the last BD in the ring, start at the beginning again.
        */
        if (bdp->cbd_sc & BD_ENET_TX_WRAP)
                bdp = cep->tx_bd_base;
        else
                bdp++;

        if (bdp->cbd_sc & BD_ENET_TX_READY) {
                netif_stop_queue(dev);
                cep->tx_full = 1;
        }

        cep->cur_tx = (cbd_t *)bdp;

        spin_unlock_irq(&cep->lock);

        return 0;
}

static void
scc_enet_timeout(struct net_device *dev)
{
        struct scc_enet_private *cep = (struct scc_enet_private *)dev->priv;

        printk("%s: transmit timed out.\n", dev->name);
        cep->stats.tx_errors++;
#ifndef final_version
        {
                int     i;
                cbd_t   *bdp;
                printk(" Ring data dump: cur_tx %p%s cur_rx %p.\n",
                       cep->cur_tx, cep->tx_full ? " (full)" : "",
                       cep->cur_rx);
                bdp = cep->tx_bd_base;
                printk(" Tx @base %p :\n", bdp);
                for (i = 0 ; i < TX_RING_SIZE; i++, bdp++)
                        printk("%04x %04x %08x\n",
                               bdp->cbd_sc,
                               bdp->cbd_datlen,
                               bdp->cbd_bufaddr);
                bdp = cep->rx_bd_base;
                printk(" Rx @base %p :\n", bdp);
                for (i = 0 ; i < RX_RING_SIZE; i++, bdp++)
                        printk("%04x %04x %08x\n",
                               bdp->cbd_sc,
                               bdp->cbd_datlen,
                               bdp->cbd_bufaddr);
        }
#endif
        if (!cep->tx_full)
                netif_wake_queue(dev);
}

/* The interrupt handler.
 * This is called from the CPM handler, not the MPC core interrupt.
 */
static irqreturn_t
scc_enet_interrupt(int irq, void *dev_id)
{
        struct  net_device *dev = dev_id;
        volatile struct scc_enet_private *cep;
        volatile cbd_t  *bdp;
        ushort  int_events;
        int     must_restart;

        cep = dev->priv;

        /* Get the interrupt events that caused us to be here.
        */
        int_events = cep->sccp->scc_scce;
        cep->sccp->scc_scce = int_events;
        must_restart = 0;

        /* Handle receive event in its own function.
        */
        if (int_events & SCCE_ENET_RXF)
                scc_enet_rx(dev_id);

        /* Check for a transmit error.  The manual is a little unclear
         * about this, so the debug code until I get it figured out.  It
         * appears that if TXE is set, then TXB is not set.  However,
         * if carrier sense is lost during frame transmission, the TXE
         * bit is set, "and continues the buffer transmission normally."
         * I don't know if "normally" implies TXB is set when the buffer
         * descriptor is closed.....trial and error :-).
         */

        /* Transmit OK, or non-fatal error.  Update the buffer descriptors.
        */
        if (int_events & (SCCE_ENET_TXE | SCCE_ENET_TXB)) {
            spin_lock(&cep->lock);
            bdp = cep->dirty_tx;
            while ((bdp->cbd_sc&BD_ENET_TX_READY)==0) {
                if ((bdp==cep->cur_tx) && (cep->tx_full == 0))
                    break;

                if (bdp->cbd_sc & BD_ENET_TX_HB)        /* No heartbeat */
                        cep->stats.tx_heartbeat_errors++;
                if (bdp->cbd_sc & BD_ENET_TX_LC)        /* Late collision */
                        cep->stats.tx_window_errors++;
                if (bdp->cbd_sc & BD_ENET_TX_RL)        /* Retrans limit */
                        cep->stats.tx_aborted_errors++;
                if (bdp->cbd_sc & BD_ENET_TX_UN)        /* Underrun */
                        cep->stats.tx_fifo_errors++;
                if (bdp->cbd_sc & BD_ENET_TX_CSL)       /* Carrier lost */
                        cep->stats.tx_carrier_errors++;


                /* No heartbeat or Lost carrier are not really bad errors.
                 * The others require a restart transmit command.
                 */
                if (bdp->cbd_sc &
                    (BD_ENET_TX_LC | BD_ENET_TX_RL | BD_ENET_TX_UN)) {
                        must_restart = 1;
                        cep->stats.tx_errors++;
                }

                cep->stats.tx_packets++;

                /* Deferred means some collisions occurred during transmit,
                 * but we eventually sent the packet OK.
                 */
                if (bdp->cbd_sc & BD_ENET_TX_DEF)
                        cep->stats.collisions++;

                /* Free the sk buffer associated with this last transmit.
                */
                dev_kfree_skb_irq(cep->tx_skbuff[cep->skb_dirty]);
                cep->skb_dirty = (cep->skb_dirty + 1) & TX_RING_MOD_MASK;

                /* Update pointer to next buffer descriptor to be transmitted.
                */
                if (bdp->cbd_sc & BD_ENET_TX_WRAP)
                        bdp = cep->tx_bd_base;
                else
                        bdp++;

                /* I don't know if we can be held off from processing these
                 * interrupts for more than one frame time.  I really hope
                 * not.  In such a case, we would now want to check the
                 * currently available BD (cur_tx) and determine if any
                 * buffers between the dirty_tx and cur_tx have also been
                 * sent.  We would want to process anything in between that
                 * does not have BD_ENET_TX_READY set.
                 */

                /* Since we have freed up a buffer, the ring is no longer
                 * full.
                 */
                if (cep->tx_full) {
                        cep->tx_full = 0;
                        if (netif_queue_stopped(dev)) {
                                netif_wake_queue(dev);
                        }
                }

                cep->dirty_tx = (cbd_t *)bdp;
            }

            if (must_restart) {
                volatile cpm_cpm2_t *cp;

                /* Some transmit errors cause the transmitter to shut
                 * down.  We now issue a restart transmit.  Since the
                 * errors close the BD and update the pointers, the restart
                 * _should_ pick up without having to reset any of our
                 * pointers either.
                 */

                cp = cpmp;
                cp->cp_cpcr =
                    mk_cr_cmd(CPM_ENET_PAGE, CPM_ENET_BLOCK, 0,
                                        CPM_CR_RESTART_TX) | CPM_CR_FLG;
                while (cp->cp_cpcr & CPM_CR_FLG);
            }
            spin_unlock(&cep->lock);
        }

        /* Check for receive busy, i.e. packets coming but no place to
         * put them.  This "can't happen" because the receive interrupt
         * is tossing previous frames.
         */
        if (int_events & SCCE_ENET_BSY) {
                cep->stats.rx_dropped++;
                printk("SCC ENET: BSY can't happen.\n");
        }

        return IRQ_HANDLED;
}

/* During a receive, the cur_rx points to the current incoming buffer.
 * When we update through the ring, if the next incoming buffer has
 * not been given to the system, we just set the empty indicator,
 * effectively tossing the packet.
 */
static int
scc_enet_rx(struct net_device *dev)
{
        struct  scc_enet_private *cep;
        volatile cbd_t  *bdp;
        struct  sk_buff *skb;
        ushort  pkt_len;

        cep = (struct scc_enet_private *)dev->priv;

        /* First, grab all of the stats for the incoming packet.
         * These get messed up if we get called due to a busy condition.
         */
        bdp = cep->cur_rx;

for (;;) {
        if (bdp->cbd_sc & BD_ENET_RX_EMPTY)
                break;

#ifndef final_version
        /* Since we have allocated space to hold a complete frame, both
         * the first and last indicators should be set.
         */
        if ((bdp->cbd_sc & (BD_ENET_RX_FIRST | BD_ENET_RX_LAST)) !=
                (BD_ENET_RX_FIRST | BD_ENET_RX_LAST))
                        printk("CPM ENET: rcv is not first+last\n");
#endif

        /* Frame too long or too short.
        */
        if (bdp->cbd_sc & (BD_ENET_RX_LG | BD_ENET_RX_SH))
                cep->stats.rx_length_errors++;
        if (bdp->cbd_sc & BD_ENET_RX_NO)        /* Frame alignment */
                cep->stats.rx_frame_errors++;
        if (bdp->cbd_sc & BD_ENET_RX_CR)        /* CRC Error */
                cep->stats.rx_crc_errors++;
        if (bdp->cbd_sc & BD_ENET_RX_OV)        /* FIFO overrun */
                cep->stats.rx_crc_errors++;

        /* Report late collisions as a frame error.
         * On this error, the BD is closed, but we don't know what we
         * have in the buffer.  So, just drop this frame on the floor.
         */
        if (bdp->cbd_sc & BD_ENET_RX_CL) {
                cep->stats.rx_frame_errors++;
        }
        else {

                /* Process the incoming frame.
                */
                cep->stats.rx_packets++;
                pkt_len = bdp->cbd_datlen;
                cep->stats.rx_bytes += pkt_len;

                /* This does 16 byte alignment, much more than we need.
                 * The packet length includes FCS, but we don't want to
                 * include that when passing upstream as it messes up
                 * bridging applications.
                 */
                skb = dev_alloc_skb(pkt_len-4);

                if (skb == NULL) {
                        printk("%s: Memory squeeze, dropping packet.\n", dev->name);
                        cep->stats.rx_dropped++;
                }
                else {
                        skb_put(skb,pkt_len-4); /* Make room */
                        skb_copy_to_linear_data(skb,
                                (unsigned char *)__va(bdp->cbd_bufaddr),
                                pkt_len-4);
                        skb->protocol=eth_type_trans(skb,dev);
                        netif_rx(skb);
                }
        }

        /* Clear the status flags for this buffer.
        */
        bdp->cbd_sc &= ~BD_ENET_RX_STATS;

        /* Mark the buffer empty.
        */
        bdp->cbd_sc |= BD_ENET_RX_EMPTY;

        /* Update BD pointer to next entry.
        */
        if (bdp->cbd_sc & BD_ENET_RX_WRAP)
                bdp = cep->rx_bd_base;
        else
                bdp++;

   }
        cep->cur_rx = (cbd_t *)bdp;

        return 0;
}

static int
scc_enet_close(struct net_device *dev)
{
        /* Don't know what to do yet.
        */
        netif_stop_queue(dev);

        return 0;
}

static struct net_device_stats *scc_enet_get_stats(struct net_device *dev)
{
        struct scc_enet_private *cep = (struct scc_enet_private *)dev->priv;

        return &cep->stats;
}

/* Set or clear the multicast filter for this adaptor.
 * Skeleton taken from sunlance driver.
 * The CPM Ethernet implementation allows Multicast as well as individual
 * MAC address filtering.  Some of the drivers check to make sure it is
 * a group multicast address, and discard those that are not.  I guess I
 * will do the same for now, but just remove the test if you want
 * individual filtering as well (do the upper net layers want or support
 * this kind of feature?).
 */

static void set_multicast_list(struct net_device *dev)
{
        struct  scc_enet_private *cep;
        struct  dev_mc_list *dmi;
        u_char  *mcptr, *tdptr;
        volatile scc_enet_t *ep;
        int     i, j;
        cep = (struct scc_enet_private *)dev->priv;

        /* Get pointer to SCC area in parameter RAM.
        */
        ep = (scc_enet_t *)dev->base_addr;

        if (dev->flags&IFF_PROMISC) {
        
                /* Log any net taps. */
                printk("%s: Promiscuous mode enabled.\n", dev->name);
                cep->sccp->scc_psmr |= SCC_PSMR_PRO;
        } else {

                cep->sccp->scc_psmr &= ~SCC_PSMR_PRO;

                if (dev->flags & IFF_ALLMULTI) {
                        /* Catch all multicast addresses, so set the
                         * filter to all 1's.
                         */
                        ep->sen_gaddr1 = 0xffff;
                        ep->sen_gaddr2 = 0xffff;
                        ep->sen_gaddr3 = 0xffff;
                        ep->sen_gaddr4 = 0xffff;
                }
                else {
                        /* Clear filter and add the addresses in the list.
                        */
                        ep->sen_gaddr1 = 0;
                        ep->sen_gaddr2 = 0;
                        ep->sen_gaddr3 = 0;
                        ep->sen_gaddr4 = 0;

                        dmi = dev->mc_list;

                        for (i=0; i<dev->mc_count; i++) {
                
                                /* Only support group multicast for now.
                                */
                                if (!(dmi->dmi_addr[0] & 1))
                                        continue;

                                /* The address in dmi_addr is LSB first,
                                 * and taddr is MSB first.  We have to
                                 * copy bytes MSB first from dmi_addr.
                                 */
                                mcptr = (u_char *)dmi->dmi_addr + 5;
                                tdptr = (u_char *)&ep->sen_taddrh;
                                for (j=0; j<6; j++)
                                        *tdptr++ = *mcptr--;

                                /* Ask CPM to run CRC and set bit in
                                 * filter mask.
                                 */
                                cpmp->cp_cpcr = mk_cr_cmd(CPM_ENET_PAGE,
                                                CPM_ENET_BLOCK, 0,
                                                CPM_CR_SET_GADDR) | CPM_CR_FLG;
                                /* this delay is necessary here -- Cort */
                                udelay(10);
                                while (cpmp->cp_cpcr & CPM_CR_FLG);
                        }
                }
        }
}

/* Initialize the CPM Ethernet on SCC.
 */
static int __init scc_enet_init(void)
{
        struct net_device *dev;
        struct scc_enet_private *cep;
        int i, j, err;
        uint dp_offset;
        unsigned char   *eap;
        unsigned long   mem_addr;
        bd_t            *bd;
        volatile        cbd_t           *bdp;
        volatile        cpm_cpm2_t      *cp;
        volatile        scc_t           *sccp;
        volatile        scc_enet_t      *ep;
        volatile        cpm2_map_t              *immap;
        volatile        iop_cpm2_t      *io;

        cp = cpmp;      /* Get pointer to Communication Processor */

        immap = (cpm2_map_t *)CPM_MAP_ADDR;     /* and to internal registers */
        io = &immap->im_ioport;

        bd = (bd_t *)__res;

        /* Create an Ethernet device instance.
        */
        dev = alloc_etherdev(sizeof(*cep));
        if (!dev)
                return -ENOMEM;

        cep = dev->priv;
        spin_lock_init(&cep->lock);

        /* Get pointer to SCC area in parameter RAM.
        */
        ep = (scc_enet_t *)(&immap->im_dprambase[PROFF_ENET]);

        /* And another to the SCC register area.
        */
        sccp = (volatile scc_t *)(&immap->im_scc[SCC_ENET]);
        cep->sccp = (scc_t *)sccp;              /* Keep the pointer handy */

        /* Disable receive and transmit in case someone left it running.
        */
        sccp->scc_gsmrl &= ~(SCC_GSMRL_ENR | SCC_GSMRL_ENT);

        /* Configure port C and D pins for SCC Ethernet.  This
         * won't work for all SCC possibilities....it will be
         * board/port specific.
         */
        io->iop_pparc |=
                (PC_ENET_RENA | PC_ENET_CLSN | PC_ENET_TXCLK | PC_ENET_RXCLK);
        io->iop_pdirc &=
                ~(PC_ENET_RENA | PC_ENET_CLSN | PC_ENET_TXCLK | PC_ENET_RXCLK);
        io->iop_psorc &=
                ~(PC_ENET_RENA | PC_ENET_TXCLK | PC_ENET_RXCLK);
        io->iop_psorc |= PC_ENET_CLSN;

        io->iop_ppard |= (PD_ENET_RXD | PD_ENET_TXD | PD_ENET_TENA);
        io->iop_pdird |= (PD_ENET_TXD | PD_ENET_TENA);
        io->iop_pdird &= ~PD_ENET_RXD;
        io->iop_psord |= PD_ENET_TXD;
        io->iop_psord &= ~(PD_ENET_RXD | PD_ENET_TENA);

        /* Configure Serial Interface clock routing.
         * First, clear all SCC bits to zero, then set the ones we want.
         */
        immap->im_cpmux.cmx_scr &= ~CMX_CLK_MASK;
        immap->im_cpmux.cmx_scr |= CMX_CLK_ROUTE;

        /* Allocate space for the buffer descriptors in the DP ram.
         * These are relative offsets in the DP ram address space.
         * Initialize base addresses for the buffer descriptors.
         */
        dp_offset = cpm_dpalloc(sizeof(cbd_t) * RX_RING_SIZE, 8);
        ep->sen_genscc.scc_rbase = dp_offset;
        cep->rx_bd_base = (cbd_t *)cpm_dpram_addr(dp_offset);

        dp_offset = cpm_dpalloc(sizeof(cbd_t) * TX_RING_SIZE, 8);
        ep->sen_genscc.scc_tbase = dp_offset;
        cep->tx_bd_base = (cbd_t *)cpm_dpram_addr(dp_offset);

        cep->dirty_tx = cep->cur_tx = cep->tx_bd_base;
        cep->cur_rx = cep->rx_bd_base;

        ep->sen_genscc.scc_rfcr = CPMFCR_GBL | CPMFCR_EB;
        ep->sen_genscc.scc_tfcr = CPMFCR_GBL | CPMFCR_EB;

        /* Set maximum bytes per receive buffer.
         * This appears to be an Ethernet frame size, not the buffer
         * fragment size.  It must be a multiple of four.
         */
        ep->sen_genscc.scc_mrblr = PKT_MAXBLR_SIZE;

        /* Set CRC preset and mask.
        */
        ep->sen_cpres = 0xffffffff;
        ep->sen_cmask = 0xdebb20e3;

        ep->sen_crcec = 0;      /* CRC Error counter */
        ep->sen_alec = 0;       /* alignment error counter */
        ep->sen_disfc = 0;      /* discard frame counter */

        ep->sen_pads = 0x8888;  /* Tx short frame pad character */
        ep->sen_retlim = 15;    /* Retry limit threshold */

        ep->sen_maxflr = PKT_MAXBUF_SIZE;   /* maximum frame length register */
        ep->sen_minflr = PKT_MINBUF_SIZE;  /* minimum frame length register */

        ep->sen_maxd1 = PKT_MAXBLR_SIZE;        /* maximum DMA1 length */
        ep->sen_maxd2 = PKT_MAXBLR_SIZE;        /* maximum DMA2 length */

        /* Clear hash tables.
        */
        ep->sen_gaddr1 = 0;
        ep->sen_gaddr2 = 0;
        ep->sen_gaddr3 = 0;
        ep->sen_gaddr4 = 0;
        ep->sen_iaddr1 = 0;
        ep->sen_iaddr2 = 0;
        ep->sen_iaddr3 = 0;
        ep->sen_iaddr4 = 0;

        /* Set Ethernet station address.
         *
         * This is supplied in the board information structure, so we
         * copy that into the controller.
         */
        eap = (unsigned char *)&(ep->sen_paddrh);
        for (i=5; i>=0; i--)
                *eap++ = dev->dev_addr[i] = bd->bi_enetaddr[i];

        ep->sen_pper = 0;       /* 'cause the book says so */
        ep->sen_taddrl = 0;     /* temp address (LSB) */
        ep->sen_taddrm = 0;
        ep->sen_taddrh = 0;     /* temp address (MSB) */

        /* Now allocate the host memory pages and initialize the
         * buffer descriptors.
         */
        bdp = cep->tx_bd_base;
        for (i=0; i<TX_RING_SIZE; i++) {

                /* Initialize the BD for every fragment in the page.
                */
                bdp->cbd_sc = 0;
                bdp->cbd_bufaddr = 0;
                bdp++;
        }

        /* Set the last buffer to wrap.
        */
        bdp--;
        bdp->cbd_sc |= BD_SC_WRAP;

        bdp = cep->rx_bd_base;
        for (i=0; i<CPM_ENET_RX_PAGES; i++) {

                /* Allocate a page.
                */
                mem_addr = __get_free_page(GFP_KERNEL);
                /* BUG: no check for failure */

                /* Initialize the BD for every fragment in the page.
                */
                for (j=0; j<CPM_ENET_RX_FRPPG; j++) {
                        bdp->cbd_sc = BD_ENET_RX_EMPTY | BD_ENET_RX_INTR;
                        bdp->cbd_bufaddr = __pa(mem_addr);
                        mem_addr += CPM_ENET_RX_FRSIZE;
                        bdp++;
                }
        }

        /* Set the last buffer to wrap.
        */
        bdp--;
        bdp->cbd_sc |= BD_SC_WRAP;

        /* Let's re-initialize the channel now.  We have to do it later
         * than the manual describes because we have just now finished
         * the BD initialization.
         */
        cpmp->cp_cpcr = mk_cr_cmd(CPM_ENET_PAGE, CPM_ENET_BLOCK, 0,
                        CPM_CR_INIT_TRX) | CPM_CR_FLG;
        while (cp->cp_cpcr & CPM_CR_FLG);

        cep->skb_cur = cep->skb_dirty = 0;

        sccp->scc_scce = 0xffff;        /* Clear any pending events */

        /* Enable interrupts for transmit error, complete frame
         * received, and any transmit buffer we have also set the
         * interrupt flag.
         */
        sccp->scc_sccm = (SCCE_ENET_TXE | SCCE_ENET_RXF | SCCE_ENET_TXB);

        /* Install our interrupt handler.
        */
        request_irq(SIU_INT_ENET, scc_enet_interrupt, 0, "enet", dev);
        /* BUG: no check for failure */

        /* Set GSMR_H to enable all normal operating modes.
         * Set GSMR_L to enable Ethernet to MC68160.
         */
        sccp->scc_gsmrh = 0;
        sccp->scc_gsmrl = (SCC_GSMRL_TCI | SCC_GSMRL_TPL_48 | SCC_GSMRL_TPP_10 | SCC_GSMRL_MODE_ENET);

        /* Set sync/delimiters.
        */
        sccp->scc_dsr = 0xd555;

        /* Set processing mode.  Use Ethernet CRC, catch broadcast, and
         * start frame search 22 bit times after RENA.
         */
        sccp->scc_psmr = (SCC_PSMR_ENCRC | SCC_PSMR_NIB22);

        /* It is now OK to enable the Ethernet transmitter.
         * Unfortunately, there are board implementation differences here.
         */
        io->iop_pparc &= ~(PC_EST8260_ENET_LOOPBACK |
                                PC_EST8260_ENET_SQE | PC_EST8260_ENET_NOTFD);
        io->iop_psorc &= ~(PC_EST8260_ENET_LOOPBACK |
                                PC_EST8260_ENET_SQE | PC_EST8260_ENET_NOTFD);
        io->iop_pdirc |= (PC_EST8260_ENET_LOOPBACK |
                                PC_EST8260_ENET_SQE | PC_EST8260_ENET_NOTFD);
        io->iop_pdatc &= ~(PC_EST8260_ENET_LOOPBACK | PC_EST8260_ENET_SQE);
        io->iop_pdatc |= PC_EST8260_ENET_NOTFD;

        dev->base_addr = (unsigned long)ep;

        /* The CPM Ethernet specific entries in the device structure. */
        dev->open = scc_enet_open;
        dev->hard_start_xmit = scc_enet_start_xmit;
        dev->tx_timeout = scc_enet_timeout;
        dev->watchdog_timeo = TX_TIMEOUT;
        dev->stop = scc_enet_close;
        dev->get_stats = scc_enet_get_stats;
        dev->set_multicast_list = set_multicast_list;

        /* And last, enable the transmit and receive processing.
        */
        sccp->scc_gsmrl |= (SCC_GSMRL_ENR | SCC_GSMRL_ENT);

        err = register_netdev(dev);
        if (err) {
                free_netdev(dev);
                return err;
        }

        printk("%s: SCC ENET Version 0.1, ", dev->name);
        for (i=0; i<5; i++)
                printk("%02x:", dev->dev_addr[i]);
        printk("%02x\n", dev->dev_addr[5]);

        return 0;
}

module_init(scc_enet_init);